Composite sheet material



Oct. 27, 1931. G. A. R|HTER 1,829,157

COMPOSITE SHEET MATERIAL Filed Sept. 29, 1928 Patented Oct. 27, 1931UNITED STATES PATENT OFFICE GEORGE A. RICHTER, OF BERLIN, NEWHAMLPSHIRE, ASSIGNOR TO BROWN COMPANY, DIE BERLIN, NEW'HAMPSEERE, ACORPORATION OF IvIAIN'E COMPOSITE SHEET MATERIAL This invention dealswith the manufacture of composite sheet material made of plies ofcellulose fibers having diflerent characteristics and intended for useas a raw material in the production ofvarious products.

When cellulose fiber such as wood-pulp is used asa raw material in themanufacture of webs designed for treatment with liquid materials, suchas liquid impregnating agents or chemical solutions, it has sometimesbeen found desirable to felt the fibers in substantially unbeatencondition on machinery of the papermaking type into a more or lessfluffy web capable of being rapidly and uniformly penetrated by theliquid material and of absorbing a large amount of such mate rial. Byusing the pulp in substantially unbeaten condition, the fibers may beloosely felted into a light, fiuify web or waterlaid sheet of highabsorptivity, particularly when the original pulp is of highabsorptivity and is felted and dried without being subjected tosubstantial pressures, such as .used in cus-- tomary papermakingpractice. One serious disadvantage of awaterlaidweb so made,however, isthat it is unsuitable for use as a raw material in a process whichplaces it under much stress as it tends to break. In accordance with thepresent invention, this disad-' vantage is overcome by adhesivelyuniting it face to face with a much stronger web of paper to produce acomposite sheet of sufiicient strength to be handled without breakingunder the stresses to which it is subjected in the usual treatments withliquid materials. If desired, two flufiy webs may be so united with theopposite faces of a paper web to produce a composite sheet which isinteriorly reinforced. Where a composite sheet is produced as describedwith a paper web formed of gelatinized pulp, produced for example byhard-beating, it may be made of suflicfent strength, for instance, to bedrawn through baths of liquid treating material quite satisfactorily,the material rapidly penetrating through and being absorbed in largequantity by the fluffy web material. For instance, when the compositesheet is passed through a rubber-containing bath, e. g. rubber latex, anartificial aqueous rubber dis- For instance, whereas the breaking lengthof the rubber-impregnated, fiuify web alone may be about 1,000 to 1,500yards, the breaking length of the paper web impregnated with a lowerproportion of rubber maybe about4,000 yards, so that the compositesheet, after impregnation, may have a breaking length of about 2,500 to4,000 yards, andthus compare favorably with leather which may have abreaking length Breaking length is the length of paper which if freelysuspended would break as a result of its own weight. The fluffy web,material after impregnation with agents such as rubber or lacquers ofthe nitrocellulose type, affords an excellent embossing surface, owingto the permanent displacement or give in 'the material under embossingaction before the impregnating agent sets.

With these and other features in view, the invention may be bestunderstood from the following more complete description thereof whenconsidered in conjunction with the accompanying drawings, wherein Figure1 illustrates more or less diagrammatically and conventionally a methodof forming a two-ply composite sheet.

Figure 2 illustrates a method of forming and treating a three-plycomposite sheet.

Figures 3 and 4 show in perspective impregnated and embossed fragmentsof composite sheets produced respectively as illustrated in Figures 1and 2.

Referring to Figure 1 of the drawings, 1 represents a rolled fluffy webof felted cellulose fibers, and 2 a rolled paper web, these webs havingthe characteristics hereinbefore described. Both webs may besimultaneous- 1y unwound, the paper web being treated of about 3,000yards.

with suitable adhesive on its upper face, as

by an adhesive-applying roll 3, whereupon the two webs may be unitedface to face un-., der a roll 4. Or an internally reinforced, compositesheet may be formed as illustrated in Figure 2, two rolled fluify webs 5and a rolled paper web 6 beingsimultaneously unwound, the paper webbeing treated with three-ply sheet taking a downward loop extending froma roll 10, under a roll 11 in a bath of liquid material 9, to a roll 12.If

, the sheet is being treated in an aqueous bath the characterdescribed,as it is not necessary lose, such as shellac.

minutes.

or in one "containing an organic solvent, the liquid content of thesheetmay be removed by passing it over one or more heating rolls 13, but ifthe bath is made up of molten thermoplastic impregnating agents such asasphalt, waxes, or the like, the rolls 13 may be cooled to congeal theseagents in the sheet.

Cellulose fibers of various origins may be employed in producing acomposite sheet of that the fiuify ply and the paper ply be made withfiber of the same origin. Preferably, a refined wood fiber of high alphacellulose content in substantially unbeaten condition is employed as theraw material for making the fluffy web, as the resulting web is ofespecially high absorptivity, owing not only to the loosely feltedcondition of the fibers, but also to the high absorptivity of the fiberitself.-

lhe paper web may be formed of similar beaten fiber, or from rag,sulphite, kraft, or manila stock, the fiber being well beaten to producepaper of the desired strength. Thus, whereas the substantially unbeatenfiber employed as a raw material for the flufi'y web may have a slownessof about one minute, the beaten fiber employed for. making the paper webmay have a slowness of about forty The paper web may also containv theusual sizing or filling materials, or may be impregnated before beingunited with one or more fiuify webs as described, the impregnatingmaterial being similar to or different from a material subsequently usedfor impregnating the composite sheet. When the paper web is-to beimpregnated with a material such as rubber, which does not bond wellwith a material such as nitrocellulose with which the composite sheet isto be impregnated, the adhesive employed for uniting the webs ispreferably one which efiects a good bond between rubber and nitrocellu-A composite sheet such as described may of cellulose derivative'such asv1scose,whereupon, if desired, regenerated cellulose may be produced insit-u in the sheet by passing it through a cellulose-regeneratingsolutlon such as a niter' cake solution, and the sheet then washed anddried. Or it may be passed through baths of parchmentizing reagents suchas a zinc chloride or a sulphuric acid solution, then washed and dried.

Having thus described certain embodiments of this invention, it shouldbe evident to those skilled in the art that various changes andmodifications might be made therein without departing from the spiritand scopeof invention as defined by the appended claims.

I claim:

1. Com osite sheet material comprising a waterlald ply of substantiallyunbeaten cellulose fibers in a loosely felted condition, and a ply ofcellulose fibers bonded together with gelatinized cellulose.

2. Composite sheet material comprising a waterlaid ply of substantiallyunbeaten wood fibers of high alpha cellulose content in a loosely feltedcondition, and a much stronger ply of cellulose fibers bonded togetherwith gelatinized cellulose.

3. impregnated composite sheet material comprising a ply ofsubstantially unbeaten fibers in a loosely felted condition, and a paperply, one of the plies carrying rubber as the impregnating agent and theother carrying nitrocellulose.

4:. impregnated composite sheet material comprising a ply ofsubstantially unbeaten fibers in a loosely felted condition, and a paperply, one of the plies carrying rubber as the impregnating agent and theother carrying nitrocellulose, said plies being .united by an adhesivebonding the rubber to the nitrocellulose.

5.-l[mpregnated composite sheet material comprising a ply ofsubstantially unbeaten condition and a ply of cellulose fibers bondedtogether with gelatinized cellulose, the ply ofsubstantially unbeatencellulose fibers car- -ry1ng a ma ing agent.

jor proportion of the impregnat- In testimony whereof I have aflixe d mysignature.

GEORGE A. RICHTER.

